The present invention relates to a system for automation of a metal machining center, such as a turning center, and more particularly to such a center which eliminates most operator intervention during automatic machining operations.
Attempts have been made to automate machining and work quality verification operations on the same machine, sucn as a lathe. Any practical form of automation requires automatic tool changing capability, and some degree of automation has been achieved by utilizing rotating turrets or other forms of tool storage magazines, and when quality verification is desired this creates a need for the ability to verify the measuring process itself.
For example, in automatic turret lathes a plurality of tools are located on one or more rotatable turrets supported on the cross slide, and the turret can be rotated to bring into an active position any one of the tools fixed to the turret. Of course, the turret and all its moving parts are constantly exposed to chips from the workpiece being machined with the possibility that chips will lodge in the moving parts, resulting in the turret jamming or the tool becoming misaligned in some way that the required accuracy is not attained during machining operations. If any of these things occur during automatic operations, an operator is required to stop the cycle and intervene to correct the stoppage prior to resuming operations, or else the workpiece operated on will become scrap.
Another type tool changing device used, for example, in an automatic horizontal spindle chucker, provides a tool magazine at a fixed location on the main frame of the machine for storing a plurality of tools which can be exchanged with an active tool in an appropriate holder on the cross slide. This requires the cross slide to be moved to a position adjacent the magazine during the transfer of tools and/or probes between the magazine and the actve tool holder mounted on the cross slide. Since this tool exchange requires a substantial amount of time, particularly in traversing the slide and re-orienting the active tool holder toward the tool magazine, the full benefit of automatic operations is not achieved.
Additionally, any machine which incorporates tool changing normally uses some type of tool magazine or store and cutting tools which are all fitted to commonly dimensioned tool carriers. The tool holder on the slide, for supporting a selected cutting tool, is fitted with an appropriate socket into which any carrier can be engaged, and such socket is generally prone to having debris such as metal chips becoming lodged therein, as well as catching on other parts of the tool holder. This can interfere with maintaining the proper alignment of the working tool due, for example, to such debris becoming lodged in the socket of the tool holder and causing misalignment of the tool, introducing error into the machining operation which may not be readily detected.
Further, during extended automatic operations metal chips, other debris, and contaminated coolant can also collect on the bed and the ways, as well as the tool changer and other operating portions of the lathe. In addition to presenting an ongoing maintenance problem, this condition can affect the alignment and free movement of the cross slide, its carriage, the ways, and any ram or the like fitted to the slide, and cause damaging wear to all these parts.
When quality verification is introduced, as by utilizing checking probes or the like fitted to the tool holder instead of a tool, the same problems spill over into the measuring/verifying process, and can be just as critical in that respect. Further, when utilizing probing techniques for automatically determining the machining quality, especially with conventional horizontal spindle lathes or "chucker" designs, due to the machine configuration, excessive yaw, pitch and roll of the mechanical slides may tend to cause variances beyond allowable tolerances in the workpieces machined. Specifically, it has been found that conventional spacing between the bearing ways to the tool center line and from the tool slide way to the workpiece, along with a standard guide way width, do not provide the required vertical and horizontal stability.
When using checking probes, mounted in the tool holder, for work quality verification, it is highly desirable that the slides, their drives, etc. be as close to possible in the same postion of extension/retraction when the probes are verified as when they are actually probing a workpiece. To accomplish this on a conventionally constructed lathe or "chucker" is not feasible to the elongated bed layout of such machines. Verification usually must occur at the opposite end of the bed ways from the chuck or other workpiece holder, e.g. from the machining area.
Accordingly, there is a need for an automatic machining center system for lathes and other turning tools which, during extended automatic machining operations, will achieve the required close tolerance and machining accuracy in less time while requiring little if any operator intervention.